Abstract
In recent years, imitation has played a central role in conceptions of children’s memory, representational, and social cognitive abilities; in nonhuman primate cognitive competencies; and the evolution of human culture. In this paper, we combine data from three studies that assessed deferred imitation in three juvenile, enculturated (human-reared) chimpanzees (
Pan troglodytes), administered over a 4-year period, to assess the development of deferred imitation. The basic task used in each study involved a baseline, followed by a demonstration in which a model displayed some actions on objects to participants. After a 10-min delay, the participants were given the objects and evidence of imitation was noted. The number of trials on which chimpanzees displayed deferred imitation increased with age, both between and within participants. Developmental differences were most apparent on the more complex tasks that required coordination of actions on materials (e.g., putting a nail in form board and striking it with a hammer) than on simpler tasks (e.g., striking two cymbals together). Patterns of performance were similar when the complete set of actions (targets) were duplicated by the ape and when the ape duplicated only portions of the demonstrated behavior (approximation to the target). The results were interpreted as reflecting age-related changes in chimpanzees’ abilities to engage in complex social learning after a delay, and arguably in the symbolic representational system supporting such abilities.